Systems and methods for imaging large field-of-view objects

ABSTRACT

An imaging apparatus and related method comprising a detector located a distance from a source and positioned to receive a beam of radiation in a trajectory; a detector positioner that translates the detector to an alternate position in a direction that is substantially normal to the trajectory; and a beam positioner that alters the trajectory of the radiation beam to direct the beam onto the detector located at the alternate position.

This application is a reissue of U.S. Pat. No. 9,724,058 issued on Aug.8, 2017. The disclosures of the above application is incorporated hereinby reference.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.14/223,361 filed on Mar. 24, 2014, which is a continuation of U.S.patent application Ser. No. 12/684,430 filed on Jan. 8, 2010, now U.S.Pat. No. 8,678,647 issued on Feb. 16, 2010, which is a continuation ofU.S. patent application Ser. No. 11/522,794 filed on Sep. 18, 2006, nowU.S. Pat. No. 7,661,882 issued on Feb. 16, 2010, which is a continuationof U.S. patent application Ser. No. 10/392,365 filed on Mar. 18, 2003,now U.S. Pat. No. 7,108,421 issued on Sep. 19, 2006, which claimsbenefit of U.S. Patent Application No. 60/366,062 filed on Mar. 19,2002. The entire disclosures of each of the above applications areincorporated herein by reference.

Notice: More than one reissue application has been filed for the reissueof U.S. Pat. No. 9,724,058. The reissue applications are U.S. patentapplication Ser. No. 16/531,388 (the present application); U.S. patentapplication Ser. No. 16/532,892 which is a continuation reissue of U.S.patent application Ser. No. 16/531,388, now abandoned; and U.S. patentapplication Ser. No. 29/701,004, which is a continuation U.S. patentapplication Ser. No. 16/532,892.

FIELD

The present disclosure relates to a system for imaging a subject, andparticularly to a system for detecting image radiation.

BACKGROUND

This section provides background information related to the presentdisclosure which is not necessarily prior art.

In conventional computerized tomography for both medical and industrialapplications, an x-ray fan beam and a linear array detector are employedto achieve two-dimensional axial imaging. The quality of thesetwo-dimensional (2D) images is high, although only a single slice of anobject can be imaged at a time. To acquire a three-dimensional (3D) dataset, a series of 2D images are sequentially obtained in what is known asthe “stack of slices” technique. One drawback to this method is thatacquiring the 3D data set one slice at a time is an inherently slowprocess. There are other problems with this conventional tomographictechnique, such as motion artifacts arising from the fact that theslices cannot be imaged simultaneously, and excessive exposure to x-rayradiation due to overlap of the x-ray projection areas.

Another technique for 3D computerized tomography is cone-beam x-rayimaging. In a system employing cone-beam geometry, an x-ray sourceprojects a cone-shaped beam of x-ray radiation through the target objectand onto a 2D area detector area. The target object is scanned,preferably over a 360-degree range, either by moving the x-ray sourceand detector in a scanning circle around the stationary object, or byrotating the object while the source and detector remain stationary. Ineither case, it is the relative movement between the source and objectwhich accomplishes the scanning. Compared to the 2D “stack of slices”approach for 3D imaging, the cone-beam geometry is able to achieve 3Dimages in a much shorter time, while minimizing exposure to radiation.One example of a cone beam x-ray system for acquiring 3D volumetricimage data using a flat panel image receptor is discussed in U.S. Pat.No. 6,041,097 to Roos, et al.

A significant limitation of existing cone-beam reconstruction techniquesoccurs, however, when the object being imaged is larger than thefield-of-view of the detector, which is a quite common situation in bothindustrial and medical imaging applications. In this situation, somemeasured projections contain information from both the field of view ofinterest and from other regions of the object outside the field of view.The resulting image of the field of view of interest is thereforecorrupted by data resulting from overlying material.

Several approaches have been proposed for imaging objects larger thanthe field-of-view of the imaging system. U.S. Pat. No. 5,032,990 toEberhard et al., for example, discusses a technique for 2D imaging of anobject which is so wide that a linear array detector is not wide enoughto span the object or part which is to be viewed. The method involvessuccessively scanning the object and acquiring partial data sets at aplurality of relative positions of the object, x-ray source, anddetector array. U.S. Pat. No. 5,187,659 to Eberhard et al. discusses atechnique for avoiding corrupted data when performing 3D CT on an objectlarger than the field of view. This technique involves scanning theobject with multiple scanning trajectories, using one or more x-raysources and detectors which rotate in different trajectories relative tothe target object. Yet another technique is discussed in U.S. Pat. No.5,319,693 to Ebarhard et al. This patent discusses simulating arelatively large area detector using a relatively small area detector byeither moving the actual area detector relative to the source, or movingthe object relative to the area detector. All of these techniques arecharacterized by complex relative movements between one or more x-raysources, detectors, and the object being imaged. Furthermore, in each ofthese techniques, the target object is exposed to excessive x-rayradiation from regions of overlapping projections.

To date, there does not exist a radiation system for imaging largefield-of-view objects in a simple and straightforward manner whileminimizing the target object's exposure to radiation.

SUMMARY

This section provides a general summary of the disclosure, and is not acomprehensive disclosure of its full scope or all of its features.

The present invention relates to radiation-based imaging, including 3Dcomputerized tomography (CT) and 2D planar x-ray imaging. In particularthis invention relates to methods and systems for minimizing the amountof missing data and, at the same time, avoiding corrupted and resultingartifacts in image reconstruction when a cone-beam configuration is usedto image a portion of an object that is larger than the field of view.

An imaging apparatus according to one aspect comprises a source thatprojects a beam of radiation in a first trajectory; a detector located adistance from the source and positioned to receive the beam of radiationin the first trajectory; an imaging area between the source and thedetector, the radiation beam from the source passing through a portionof the imaging area before it is received at the detector; a detectorpositioner that translates the detector to a second position in a firstdirection that is substantially normal to the first trajectory; and abeam positioner that alters the trajectory of the radiation beam todirect the beam onto the detector located at the second position. Theradiation source can be an x-ray cone-beam source, and the detector canbe a two-dimensional flat-panel detector array.

By translating a detector of limited size along a line or arc oppositethe radiation source, and obtaining object images at multiple positionsalong the translation path, an effectively large field-of-view may beachieved. In one embodiment, a detector positioner for translating thedetector comprises a positioner frame that supports the detector anddefines a translation path, and a motor that drives the detector as ittranslates within the positioner frame. A positioning feedback system,which can include a linear encoder tape and a read head, can be used toprecisely locate and position the detector within the positioner frame.Other position encoder systems could also be used as the positioningfeedback system, such as a rotary encoder and a friction wheel.

A radiation source, such as an x-ray source, includes a beam positioningmechanism for changing the trajectory of the emitted radiation beam froma fixed focal spot. This enables the beam to scan across an imagingregion, and follow the path of a moving target, such as a translatingdetector array. In one aspect, the beam positioning mechanism of thepresent invention enables safer and more efficient dose utilization, asthe beam positioner permits the beam to sequentially scan throughlimited regions of the target object, so that only the region within thefield-of-view of the translating detector at any given time need beexposed to harmful radiation.

In one embodiment, a tilting beam positioning mechanism includes a framewhich houses the radiation source, and a motorized system connected toboth the frame and the source, where the motorized system pivots ortilts the source relative to the frame to alter the trajectory of theradiation beam projected from the source. In a preferred embodiment, thesource is pivoted about the focal spot of the projected radiation beam.The motorized tilting system could include, for example, a linearactuator connected at one end to the fixed frame and at the other end tothe source, where the length of the actuator controls the angle of tiltof the source, or a motorized pulley system for tilting the source. Inanother embodiment, a movable collimator is driven by a motor forchanging the trajectory of the output beam.

In still another aspect, the invention includes means for rotating thesource and translatable detector relative to an object to obtain imagesat different projection angles over a partial of full 360-degree scan.In one embodiment, the source and detector are housed in a gantry, suchas a substantially O-shaped gantry ring, and are rotatable around theinside of the gantry ring. The source and detector can be mounted to amotorized rotor which rotates around the gantry on a rail and bearingsystem. In another embodiment, the source and translatable detectorremain fixed on a support, such as a table, while the object rotates ona turntable or rotatable stage.

The invention also relates to a method of imaging an object comprisingprojecting a beam of radiation in a first trajectory, the beam travelingthrough a first region of the object and onto a detector located at afirst position; translating the detector to a second position in adirection that is substantially normal to the first trajectory; andaltering the trajectory of the beam so that the beam travels through asecond region of the object and onto the detector located at the secondposition. Preferably, the beam of radiation comprises a cone-beam orfan-beam of x-ray radiation, and the detected radiation is used toproduce two-dimensional planar or three-dimensional computerizedtomographic (CT) object images.

In one aspect, the invention is able to image objects larger than thefield-of-view of the detector in a simple and straightforward manner byutilizing a detector positioner that translates the detector array tomultiple positions, thus providing an effectively large field-of-viewusing only a single detector array having a relatively small size. Inaddition, a beam positioner permits the trajectory of the beam to followthe path of the translating detector, which advantageously enables saferand more efficient dose utilization, as only the region of the targetobject that is within the field-of-view of the detector at any giventime needs to be exposed to harmful radiation.

Further areas of applicability will become apparent from the descriptionprovided herein. The description and specific examples in this summaryare intended for purposes of illustration only and are not intended tolimit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure.

FIGS. 1A-C are schematic diagrams showing an x-ray scanning system witha translating detector array according to one embodiment of theinvention;

FIGS. 2A-D are side and perspective views illustrating the x-ray sourceand detector of the system of FIG. 1 ;

FIG. 3 illustrates the wide field-of-view achievable with thetranslating detector system of the present invention;

FIG. 4 is a schematic diagram showing a data collection matrix of anx-ray scanner system according to one embodiment of the invention;

FIG. 5 is an exploded view of an x-ray detector positioning stageaccording to one embodiment;

FIGS. 6A-C shows the x-ray detector positioning stage translating tothree positions;

FIG. 7 is an exploded view of an x-ray source and source positioningstage according to one embodiment of the invention;

FIG. 8 is a perspective view of an assembled x-ray source andpositioning stage;

FIGS. 9A-C shows an x-ray source tilted to three positions by a linearactuator, according to one embodiment of the invention;

FIG. 10 shows a motorized belt and pulley system for tilting an x-raysource to multiple positions, according to another embodiment;

FIG. 11 shows a motorized sliding collimator for directing an x-ray beamto multiple detector positions, according to yet another embodiment;

FIG. 12 is a perspective view of a rotor assembly for rotating an x-raysource and detector within a gantry;

FIG. 13 is a cutaway side view showing the rotor assembly within agantry ring;

FIG. 14 is a schematic illustration of a mobile cart and gantry assemblyfor tomographic and planar imaging of large field-of-view objectsaccording to one embodiment;

FIG. 15 illustrates a table-top x-ray assembly with rotatable stage fortomographic and planar imaging of large field-of-view objects accordingto yet another embodiment; and

FIG. 16 shows a detector that is translated along a line.;

FIG. 17 is a schematic diagram showing an x-ray scanning systemaccording to one embodiment of the invention;

FIGS. 18A-18D show the x-ray scanning system of FIG. 17 acquiringquasi-simultaneous anterior/posterior and lateral images of a spinethroughout a rotation of a motorized rotor within the O-shaped x-raygantry;

FIG. 19 shows an x-ray detector array capturing multiple x-ray imagesthroughout a 360 degree rotation;

FIG. 20 illustrates a motorized rotor assembly for rotating an x-raysource and detector array within the gantry ring of an x-ray scanningdevice of the invention;

FIG. 21A is a cutaway side view of a gantry ring having a motorizedrotor assembly mounted inside the ring;

FIG. 21B is a side view of a gantry ring enclosing a motorized rotorassembly;

FIGS. 22A-22E illustrate an x-ray imaging apparatus having a cablemanagement system for rotating an x-ray source and detector array aroundthe interior of the gantry ring;

FIG. 23 shows a gantry ring positioning unit in a parked mode;

FIG. 24 shows the gantry ring positioning unit in a fully extendedlateral position;

FIG. 25 shows the gantry ring positioning unit in a fully extendedvertical position;

FIG. 26 shows the gantry ring positioning unit in a fully extended tiltposition;

FIG. 27 shows the gantry ring and positioning unit in fully extendedlateral, vertical, and tilt positions;

FIG. 28 illustrates an x-ray imaging apparatus having a vertical-axisgantry for imaging a standing or sitting patient;

FIG. 29 is a schematic diagram showing an x-ray scanning system with apartially open gantry ring according to one embodiment of the invention;

FIGS. 30A and 30B show two side views of the x-ray scanning system ofFIG. 29 with a hinged gantry segment in fully open and fully closedpositions;

FIG. 31 shows an x-ray scanning system with a detachable gantry segment;

FIG. 32 shows an x-ray scanning system with a piggy back gantry segment;

FIG. 33 shows an x-ray scanning system with a telescoping gantrysegment;

FIG. 34 shows an x-ray scanning system with a vertical lift gantrysegment;

FIG. 35 shows an x-ray scanning system with a pivoted gantry segment;

FIG. 36 illustrates a gantry ring for an x-ray scanner system with ahinged gantry segment and a latching mechanism in an open and unlockedposition;

FIG. 37 shows the gantry ring of FIG. 36 with the gantry segment andlatching mechanism and a closed and unlocked position;

FIG. 38 shows the interior of a hinged gantry segment with rail andbearing assembly and latching mechanism;

FIG. 39 shows the interior of a hinged gantry segment with rail andbearing assembly and latching mechanism;

FIG. 40 illustrates a motorized rotor assembly for rotating an x-raysource and detector array within the gantry ring of an x-ray scanningdevice of the invention;

FIGS. 41A-41C are schematic illustrations of a patient entering an x-rayscanning device through an open hinged segment of the gantry ring andthe patient inside the closed gantry ring;

FIG. 42 illustrates an x-ray imaging apparatus having a vertical-axisgantry with a detachable gantry segment for imaging a standing orsitting patient; and

FIGS. 43A-43E illustrate an x-ray imaging apparatus having a cablemanagement system for rotating an x-ray source and detector array 360°around the gantry ring.

Corresponding reference numerals indicate corresponding parts throughoutthe several views of the drawings.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference tothe accompanying drawings.

FIGS. 1A-C schematically illustrate an x-ray scanning system with atranslating detector array according to one embodiment of the invention.The scanning system shown in FIGS. 1A-C includes gantry 11, which inthis embodiment comprises a generally circular, or “O-shaped,” housinghaving a central opening into which an object being imaged is placed.The gantry 11 contains an x-ray source 13 (such as a rotating anodepulsed x-ray source) that projects a beam of x-ray radiation 15 into thecentral opening of the gantry, through the object being imaged, and ontoa detector array 14 (such as a flat panel digital detector array)located on the opposite side of the gantry. The x-rays received at thedetector 14 can then be used to produce a 2D planar or 3D tomographicobject reconstruction images using well-known techniques.

The detector 14 is translated to multiple positions along a line or arcin a direction that is generally normal to the trajectory of beam 15.This permits the detector to capture images of objects that are widerthan the field-of-view of the detector array. FIGS. 1A-1C show the largefield-of-view imaging area when the detector is translated to threepositions along an arc opposite the x-ray source. This is more clearlyillustrated in FIGS. 2A-C, which are side views of the source anddetector as the detector translates to three different positions. FIG.2D is a perspective view showing the resultant large imagingfield-of-view by combining the data obtained at all three source anddetector positions. As shown in FIGS. 2A-C, as the detector moves toeach subsequent position, the last column of detector pixels 41 ispositioned adjacent to the location of the leading column of pixels 42from the prior detector position, thereby providing a large “effective”detector having a wide field-of-view, as shown in FIG. 2D. The imageobtained is a combination of the three images abutted against oneanother, resulting in a large field-of-view using only a single detectorarray having a relatively small size. The detector 14 being translatedalong a line is illustrated in FIG. 16 .

The source 13 preferably includes a beam positioning mechanism forchanging the trajectory of the beam 15 from a stationary focal spot 40,so that the beam follows the detector as the detector translates, asshown in FIGS. 1A-C. This permits safer and more efficient doseutilization, as generally only the region of the target object that iswithin the field-of-view of the detector at any given time will beexposed to potentially harmful radiation.

Preferably, the translational movement of the detector and thetrajectory of the x-ray beam can be automatically coordinated andcontrolled by a computerized motor control system.

FIG. 3 illustrates the large field-of-view obtainable using thetranslating detector array of the present invention, as compared to thefield-of-view of the same array in a conventional static configuration.The small and large circles represent varying diameters of the regioncentered on the axis of the imaging area that is within thefield-of-view of the detector for the non-translatable and translatablearrays, respectively. The diameter of this imaging region isapproximately half the width of the detector, since the beam diverges inthe shape of a cone as it projects from the focal spot of the sourceonto the detector array. As shown in FIG. 3 , the diameter of thisimaging region can be greatly increased by translating the detectorarray and scanning the x-ray beam to multiple positions along a line orarc on the gantry.

In one aspect, the x-ray source 13 and translatable detector 14 arerotatable around the interior of the gantry, preferably on a motorizedrotor, to obtain large field-of-view x-ray images from multipleprojection angles over a partial or full 360-degree rotation. Collectionof multiple projections throughout a full 360-degree rotation results insufficient data for three-dimensional cone-beam tomographicreconstruction of the target object.

As shown in the matrix diagram of FIG. 4 , there are at least twomethods for obtaining large field-of-view images over a partial or full360-degree rotational scan of the target object. In the first method,for each rotational angle of the source and detector within the gantry,the detector is translated to two or more positions, capturing x-rayimages at each detector position. This is shown in the top row of thematrix diagram of FIG. 4 , where the x-ray source and detector stage aremaintained at Rotor Angle 0, while the detector translates on the stageto Detector Positions 1-3. The rotor carrying the x-ray source anddetector stage then rotate to a second position on the gantry, RotorAngle 1, and the detector again translates to the three detectorpositions. This process repeats as the x-ray source and detector stagerotate through N rotor positions on the gantry to obtain largefield-of-view object images over a full 360-degree scan.

In a second method, for each position of the translating detector, thesource and detector stage perform a partial of full 360-degree rotationaround the target object. This is shown in the leftmost column of thematrix diagram of FIG. 4 , where detector is maintained at DetectorPosition 1, while the source and detector stage rotate within the gantryto Rotor Angles 0 through N. Then, as shown in the center column of FIG.4 , the detector is translated to Detector Position 2, and the sourceand detector stage are again rotated to Rotor Angles 0 through N. Thisprocess is repeated for each position of the translating detector array,with the source and detector stage performing a partial or full scanaround the target object for each detector position.

Turning now to FIG. 5 , an x-ray detector positioner 100 according toone embodiment of the invention is shown in exploded form. Thepositioning stage comprises a detector carriage 101 for holding thedetector, a friction drive 102 which attaches to the detector carriage,and a positioner frame 103 upon which the detector carriage is movablymounted, The positioner frame includes two parallel side walls 104, abase 105, and a series of lateral frames 106 extending between the sidewalls. The interior of the side walls 104 include three main concentricsurfaces extending the length of the frame. On top of each side wall 104is a flat surface upon which a friction wheel 109 is driven, in thecenter is a v-groove rail on which a pair of v-groove rollers 110 ride,and on the bottom is another flat surface upon which a linear encodertape is affixed.

In the embodiment shown, the concentric radii of the components of thecurved side rails vary as a function of a circumscribed circle centeredat the focal spot of an x-ray source. The central ray or line thatconnects the focal spot to the center pixel of the detector array isessentially perpendicular to the flat face of the detector array. Bymoving the translating detector components along the defined curved siderails, the face of the detector translates tangentially to the circlecircumscribed by connecting the ray or line that connects the focal spotto the center pixel of the detector array. Other embodiments include acircle with infinite radius, in which case the curved side rails becomestraightened along a flat plane or line.

The friction drive 102 consists of a servomotor, gear head, belt drive,axle, and friction wheels 109. The friction drive is mounted to thedetector carriage 101 by brackets 107. The friction wheels 109 arepreferably spring-loaded and biased against the flat top surface of theside walls 104. The rollers 110 are mounted to brackets 107, and pressedinto the central v-grooves of the positioner side walls 104. Thev-groove rollers 110 precisely locate the detector carriage 101 as wellas allow loading from any direction, thus enabling the accuratepositioning of the translated detector array independent of gantry angleor position. The friction wheel 109 minimizes the backlash in thepositioning system. In addition, a read head 108 is located on adetector carriage bracket 107 for reading the encoder tape affixed tothe bottom flat surface of the positioner side wall 104. The read head108 provides position feedback information to the servomotor for precisepositioning of the detector carriage along the concentric axis oftravel. The x-ray detector positioner 100 can also include bearings 29attached to side walls 104 for rotating the entire detector assemblyaround the interior of a gantry, as described in further detail below.

Referring to FIGS. 6A-C, the assembled detector positioner 100 is showntranslating the detector carriage 101 to multiple positions along anarc. In operation, the detector carriage 101 and friction drive assembly102 are precisely moved by the servomotor along the concentric axis ofthe positioning frame and accurately positioned by the linear encodersystem. Three positions are shown in FIGS. 6A-C, although the detectorcarriage 101 may be precisely positioned at any point along the arcdefined by the positioner frame 103. The compact nature of the frictiondrive 102 allows for maximum translation of the detector carriage 101while the drive 102 remains completely enclosed within the positionerframe 103, and allows the distal ends of the detector carriage to extendbeyond the edge of the positioner frame (as shown in FIGS. 6A and 6C) tofurther increase the “effective” field-of-view obtainable with thedetector.

As discussed above, the imaging system of the present inventionpreferably includes a radiation source with a beam positioning mechanismfor changing the trajectory of the radiation emitted from a fixed focalspot, so that the beam may scan across multiple positions. Oneembodiment of an x-ray source stage 200 with a beam positioningmechanism is shown in FIG. 7 . The stage comprises an outer wall frame201 (shown in exploded form) which encloses the x-ray source 13, aswiveling x-ray source mount 202, and a servomotor linear actuator 203.The x-ray source is supported on the bottom by source mount 202 and fromthe sides by a pair of bushing mounts 206. The bushing mounts 206 areconnected to the outer wall frame 201 by precision dowel pins 204 thatare press-fit into bushings 205. The dowel pins 204 permit the bushingmounts 206, and thus the x-ray source 13 and source mount 202, to pivotwith respect to the outer wall frame 201 pivoting motion. This pivotingmotion is preferably centered at the focal spot of the x-ray source.

The precision servomotor linear actuator 203 is attached at one end tothe outer wall frame 201, and at the other end to the swiveling x-raysource mount 202. By varying the length of the motorized linear actuator203, the source mount 202 and x-ray source 13 can be pivoted about dowelpins 204 to tilt the x-ray source about its focal spot in a controlledmanner. The fully assembled x-ray source stage is shown in FIG. 8 .

The operation of the x-ray source and tilting beam positioning mechanismis shown in FIGS. 9A-9C. As the linear actuator moves from a fullyretracted position (FIG. 9A) to a fully extended position (FIG. 9C) thex-ray source pivots about its focal spot, thus altering the trajectoryof the emitted radiation beam. In this embodiment, the pivot pointrepresents the center of a circle with a radius defined by the distancefrom the focal spot to the center pixel of the detector array. The pivotangle is computed by determining the angle defined by the lineconnecting the focal spot of the x-ray detector and the center pixel ofthe detector array. A computerized motion control system can be used tosynchronize the x-ray source tilt angle with the position of atranslating detector array so that the x-ray beam remains centered onthe detector even as the detector translates to different positions.

Various other embodiments of an x-ray beam positioner can be employedaccording to the invention. For example, as shown in FIG. 10 , the x-raysource can be tilted to multiple positions by a motorized belt andpulley system. In another embodiment shown in FIG. 11 , the trajectoryof the x-ray beam is altered by a sliding collimator that is driven by aservomotor.

As shown in FIG. 12 , the x-ray source stage 200 and x-ray detectorpositioner 100 can be joined together by a curved bracket assembly 301to produce a C-shaped motorized rotor assembly 33. The rigid bracket 301maintains the source and detector opposed to one another, and the entirerotor assembly can be rotated inside an O-shaped x-ray gantry. The rotorassembly 33 can also include a motor 31 and drive wheel 32 attached atone end of the rotor for driving the rotor assembly around the interiorof the gantry.

FIG. 13 is a cutaway side view of a gantry 11 which contains a C-shapedmotorized rotor 33. The interior side walls of the gantry include curvedrails 27 extending in a continuous loop around the interior of thegantry. The drive wheel 32 of the rotor assembly 33 contacts the curvedrail 27 of the gantry, and uses the rail to drive the rotor assemblyaround the interior of the gantry. A rotary incremental encoder can beused to precisely measure the angular position of the rotor assemblywithin the gantry. The incremental encoder can be driven by a frictionwheel that rolls on a concentric rail located within the sidewall of thegantry. The rotor assembly 33 also includes bearings 29, which mate withthe curved rails 27 of the gantry to help guide the rotor assembly 33 asit rotates inside the gantry. The interior of the gantry ring 11 caninclude a slip ring that maintains electrical contact with the rotorassembly 33 to provide the power needed to operate the x-ray source,detector, detector positioner, and/or beam positioner, and also torotate the entire assembly within the gantry frame. The slip ring canfurthermore be used to transmit control signals to the rotor, and x-rayimaging data from the detector to a separate processing unit locatedoutside the gantry. Any or all of the functions of the slip ring couldbe performed by other means, such as a flexible cable harness attachedto the rotor, for example.

Although the rotor assembly of the preferred embodiment is a C-shapedrotor, it will be understood that other rotor configurations, such asO-shaped rotors, could also be employed. For example, a second curvedbracket 301 could be attached to close the open end of the rotor, andprovide a generally O-shaped rotor. In addition, the x-ray source anddetector could rotate independently of one another using separatemechanized systems.

An x-ray scanning system 10 according to one aspect of the inventiongenerally includes a gantry 11 secured to a support structure, whichcould be a mobile or stationary cart, a patient table, a wall, a floor,or a ceiling. As shown in FIG. 14 , the gantry 11 is secured to a mobilecart 12 in a cantilevered fashion via a ring positioning unit 20. Incertain embodiments, the ring positioning unit 20 enables the gantry 11to translate and/or rotate with respect to the support structure,including, for example, translational movement along at least one of thex-, y-, and z-axes, and/or rotation around at least one of the x- andy-axes. X-ray scanning devices with a cantilevered,multiple-degree-of-freedom movable gantry are described in commonlyowned U.S. Provisional Applications 60/388,063, filed Jun. 11, 2002, and60/405,098, filed Aug. 21, 2002, the entire teachings of which areincorporated herein by reference.

The mobile cart 12 of FIG. 14 can optionally include a power supply, anx-ray power generator, and a computer system for controlling operationof the x-ray scanning device, including translational movement of thedetector, and tilting movement of the x-ray source. The computer systemcan also perform various data processing functions, such as imageprocessing, and storage of x-ray images. The mobile cart 12 preferablyalso includes a display system 60, such as a flat panel display, fordisplaying images obtained by the x-ray scanner. The display can alsoinclude a user interface function, such as a touch-screen controller,that enables a user to interact with and control the functions of thescanning system. In certain embodiments, a user-controlled pendant orfoot pedal can control the functions of the scanning system. It will beunderstood that one or more fixed units can also perform any of thefunctions of the mobile cart 12.

The O-shaped gantry can include a segment that at least partiallydetaches from the gantry ring to provide an opening or “break” in thegantry ring through which the object to be imaged may enter and exit thecentral imaging area of the gantry ring in a radial direction. Anadvantage of this type of device is the ability to manipulate the x-raygantry around the target object, such as a patient, and then close thegantry around the object, causing minimal disruption to the object, inorder to perform x-ray imaging. Examples of “breakable” gantry devicesfor x-ray imaging are described in commonly-owned U.S. patentapplication Ser. No. 10/319,407, filed Dec. 12, 2002, now U.S. Pat. No.6,940,941, issued Sep. 6, 2005, the entire teachings of which areincorporated herein by reference.

It will also be understood that although the embodiments shown hereinclude x-ray imaging devices having O-shaped gantries, other gantryconfigurations could be employed, including broken ring shaped gantrieshaving less than full 360 degree rotational capability.

Referring to FIG. 15 , a table-top version of the large field-of-viewscanning device is depicted. In this embodiment, the connector bracket,gantry, and rotor friction drive have been replaced by a rigid tablemount 302 and a turntable 303 located in the center of the field ofview. The turntable rotates the object to be imaged in a complete360-degree rotation to capture projection images from any direction. Thedetector and source positioning assemblies 100, 200 are rigidly mounteda fixed distance from one another. The turntable 303 can be rigidlymounted to the table at any point along the ray connecting the x-rayfocal spot and the center of the detector positioning assembly. The datacollection techniques for this embodiment are essentially the same asthose described for the x-ray gantry, except that in this case, it isthe rotation of the object relative to the source and detector, ratherthan the rotation of the source and detector relative to the object,which effects the x-ray scanning.

The x-ray imaging systems and methods described herein may beadvantageously used for two-dimensional and/or three-dimensional x-rayscanning. Individual two-dimensional projections from set angles alongthe gantry rotation can be viewed, or multiple projections collectedthroughout a partial or full rotation may be reconstructed using cone orfan beam tomographic reconstruction techniques. This invention could beused for acquiring multi-planar x-ray images in a quasi-simultaneousmanner, such as described in commonly-owned U.S. patent application No.10/389,268 entitled “Systems and Methods for Quasi-SimultaneousMulti-Planar X-Ray Imaging,”, filed on Mar. 13, 2003, now U.S. Pat. No.7,188,998, issued on Mar. 13, 2007, the entire teachings of which areincorporated herein by reference. Also, the images acquired at eachdetector position could be reprojected onto virtual equilinear orequiangular detector arrays prior to performing standard filteredbackprojection tomographic reconstruction techniques, as described incommonly-owned U.S. Provisional Application No. 60/405,096, filed onAug. 21, 2002.

As discussed above, an x-ray scanning system is disclosed. The scanningsystem may include various embodiments which may include portions asdiscussed above and herein either separately or in combination. Forexample, FIG. 17 is a schematic diagram showing an x-ray scanning system10 in accordance with one embodiment of the invention. The x-rayscanning system 10 includes a gantry 11′ secured to a support structure,which could be a mobile or stationary cart, a patient table, a wall, afloor, or a ceiling. As shown in FIG. 17, the gantry 11′ is secured to amobile cart 12′ in a cantilevered fashion via a ring positioning unit20′. In certain embodiments, the ring positioning unit 20′ translatesand/or tilts the gantry 11′ with respect to the support structure toposition the gantry 11′ in any number of imaging positions andorientations.

The mobile cart 12′ of FIG. 17 can optionally include a power supply, anx-ray power generator, and a computer system for controlling operationof the x-ray scanning device and for performing image processing,storage of x-ray images, or other data processing functions. In apreferred embodiment, the computer system controls the positioning unit20′ to enable the gantry 11′ to be quickly moved to a particularuser-defined position and orientation. The computer preferably has amemory that is capable of storing positioning information relating toparticular gantry positions and/or orientations. This stored positioninginformation can be used to automatically move the gantry to apre-defined configuration upon demand.

The mobile cart 12′ preferably also includes a display system 60′, suchas a flat panel display, for displaying images obtained by the x-rayscanner. The display can also include a user interface function, such asa touch-screen controller, that enables a user to interact with andcontrol the functions of the scanning system. In certain embodiments, auser-controlled pendant or foot pedal can control the functions of thescanning system.

It will be understood that one or more fixed units can also perform anyof the functions of the mobile cart 12′.

According to one aspect, the x-ray scanning system of the invention canbe used to obtain two-dimensional x-ray images of an object, such as apatient, in multiple projection planes. In the embodiment shown in FIG.17, the gantry 11′ is a generally circular, or “O-shaped,” housinghaving a central opening into which an object being imaged is placed.The gantry 11′ contains an x-ray source 13′ (such as a rotating anodepulsed x-ray source) that projects a beam of x-ray radiation 15′ intothe central opening of the gantry, through the object being imaged, andonto a detector array 14′ (such as a flat panel digital detector array)located on the opposite side of the gantry. The x-rays received at thedetector 14′ can then be used to produce a two-dimensional image of theobject using well-known techniques.

The x-ray source 13′ is able to rotate around the interior of the gantry11′ in a continuous or step-wise manner so that the x-ray beam can beprojected through the object, and through a common isocenter, at variousangles over a partial or full 360 degree rotation. The detector array isalso rotated around the interior of the gantry, in coordination with therotation of the x-ray source, so that for each projection angle of thex-ray source, the detector array is positioned opposite the x-ray sourceon the gantry. The apparatus is thus able to obtain two-dimensionalx-ray images of the targeted object in any projection plane over apartial or full 360 degree rotation.

The x-ray system of the invention can be operated in a static or in amulti-planar mode. In a static mode, a user selects a desired imagingplane in the target object, and the x-ray source and detector arerotated to the appropriate angle within the gantry. As shown in FIG.18A, for example, the x-ray source and detector are at the top andbottom of the gantry, respectively, for acquisition of ananterior-posterior (AP) type patient image. Alternatively, or inaddition, the gantry itself can be moved by positioning or tilting thegantry relative to the target object using the gantry positioning unit20′, as shown in FIG. 27. In static mode, the x-ray scanner can acquireand display a single x-ray image of the object, or can obtain multipleimages of the object, and continuously update the display with the mostrecent image. In a preferred embodiment, the x-ray scanner obtainsmultiple object images in quick succession, and displays these images inreal time (e.g. 30 frames per second) in a “cinematic” mode.

To change the imaging plane of the object, the x-ray source and detectorcan be rotated to another angle within the gantry. As shown in FIG. 18B,for example, the source and detector rotate 90 degrees in a clockwisedirection for obtaining object images in a lateral plane. Alternativelyor in addition, translating or tilting the entire gantry to a secondposition can change the imaging plane.

In multi-planar mode, the x-ray scanner obtains a series of images frommultiple projection planes in rapid succession. The imaging systemadvantageously permits quasi-simultaneous multi-planar imaging using asingle radiation source. As shown in FIG. 18A, for example, the x-raysource 13′ and detector 14′ are initially positioned at the top andbottom of the gantry respectively and acquire a first x-ray image of thetarget object, which in this case is an anterior-posterior (AP) view ofa patients spine. The source and detector then rotate 90 degreesclockwise within the fixed gantry to obtain a second x-ray image shownin FIG. 18B, which is a lateral view of the spine. These bi-planarAP/lateral images are obtained quasi-simultaneously, as there is noappreciable delay between the acquisition of the two images, other thanthe time it takes for the source to rotate between projection angles onthe gantry. Additional AP/lateral images can be obtained andcontinuously updated by alternatively rotating the source and detectorbetween two projection angles, such as the two perpendicular projectionsshown FIGS. 18A and 18B. In a preferred embodiment, however,quasi-simultaneous multi-planar images are obtained and updated in realtime by continuously rotating the source and detector over a full 360degree rotation, obtaining images at desired rotational increments. Asshown in FIGS. 18A and 18B, for example, four bi-planar images,including two AP images, and two lateral images, can be obtained inquick succession during a single 360 degree rotation of the source anddetector. These images can be displayed individually, sequentially,side-by-side, or in any desired manner.

A further illustration of the quasi-simultaneous multi-planar imaging ofthe invention is shown in FIG. 19. Here, a rotatable detector array isshown capturing quasi-simultaneous x-ray images of ten incrementalprojection planes over a full 360 degree rotation. These images arecaptured continuously, or in a step wise fashion. They can be displayedindividually, side-by-side, sequentially in a cinematic mode, or in anydesired manner.

As shown in FIG. 17, the x-ray source 13′ and detector array 14′ can besecured to a C-shaped motorized rotor assembly 33′. The rigid rotorassembly maintains the source and detector opposed to one another whilethe entire rotor assembly rotates inside the gantry. As shown in FIGS.20 and 21A, the rotor assembly 33′ also includes a motor 31′ and drivewheel 32′ for driving the rotor assembly around the interior of thegantry. As shown in FIG. 21A, the interior side walls of the gantryinclude curved rails 27′ extending in a continuous loop around theinterior of the gantry. The drive wheel 32′ of the rotor assembly 33′contacts the curved rail 27′ of the gantry, and uses the tall to drivethe rotor assembly around the interior of the gantry. A rotaryincremental encoder can be used to precisely measure the angularposition of the rotor assembly within the gantry. The incrementalencoder can be driven by a friction wheel that tolls on a concentricrail located within the sidewall of the gantry. The rotor assembly 33′also includes bearings 29′, which mate with the curved rails 27′ of thegantry to help guide the rotor assembly 33′ as it rotates inside thegantry. The interior of the gantry ring 11′ can include a slip ring 102′that maintains electrical contact with the rotor assembly 33′ to providethe power (e.g., from external power source 101′) needed to operate thex-ray source/detector and to rotate the entire assembly within thegantry frame. The slip ring can also be used to transmit control signalsto the rotor, and x-ray imaging data from the detector to a separateprocessing unit located outside the gantry, such as the mobile can 12′of FIG. 17. Any or all of the functions of the slip ring could beperformed by other means, such as the cable management system describedbelow.

Although the rotor assembly of the preferred embodiment is a C-shapedrotor, it will be understood that other rotor configurations, such asO-shaped rotors, could also be employed. In addition, the x-ray sourceand detector could rotate independently of one another using separatemechanized systems. Moreover, the x-ray source alone can rotate, withmultiple detector arrays located at fixed positions around the interiorof the gantry.

The detector array 14′ shown in FIG. 20 comprises a two-dimensional flatpanel solid-state detector array. It will be understood, however, thatvarious detectors and detector arrays can be used in this invention,including any detector configurations used in typical diagnosticfan-beam or cone-beam imaging systems, such as C-arm fluoroscopes. Apreferred detector is a two-dimensional thin-film transistor x-raydetector using scintillator amorphous-silicon technology.

For large field-of-view imaging, the detector 14′ can be translated to,and acquire imaging data at, two or more positions along a line or arcopposite the x-ray source 13′, such as via a motorized detector rail andbearing system. Examples of such detector systems are described incommonly owned U.S. Provisional Application No. 60/366,062, filed Mar.19, 2002, the entire teachings of which are incorporated herein byreference.

FIGS. 22A-22E illustrate another embodiment of an x-ray imagingapparatus having a cable management system for rotating an x-ray sourceand detector array 360° around the interior of the gantry ring. In thisembodiment, the power for the x-ray source/detector system, as well asfor rotating the x-ray source/detector within the gantry, is provided(at least in part) by a cable harness 36′ containing one or more cables.The cable harness 36′ can also be used to transmit signals and databetween the x-ray source/detector and an external processing unit.

The cable harness 36′ is preferably housed in a flexible, linked cablecarrier 37′. One end of the carrier 37′ is fixed to a stationary object,such as the gantry 11′ or the cart. The other end of the carrier 37′ isattached to the motorized rotor assembly 33′ which contains the x-raysource 13′ and detector 14′. In the example shown in FIGS. 22A-22E, therotor 33′ starts at an initial position with the x-ray source 13′ at thebottom of the gantry and the detector 14′ at the top of the gantry (i.e.rotor angle=0°) as shown in FIG. 22A. The rotor 33′ then rotates in aclockwise direction around the interior of the gantry, as illustrated inFIG. 22B (90°° rotation), FIG. 22C (180°° rotation), FIG. 22D (270°°rotation), and FIG. 22E (360°° rotation). In FIG. 22D, the rotor 33′ hasmade a full 360°° rotation around the interior of the gantry 11′, andthe rotor is again at the initial position with the x-ray source 13′ atthe bottom of the gantry, and the detector 14′ at the top of the gantry.During the rotation, the cable carrier 37′ remains connected to both therotor 33′ and gantry 11′, and has sufficient length and flexibility topermit the rotor 33′ to easily rotate at least 360° from the startposition. To perform another 360° rotation, the rotor 33′ can rotatecounterclockwise from the end position of the prior rotation (e.g. rotorangle=360° in FIG. 22E) until the rotor 33′ returns to the initialposition of FIG. 22A. For continuous rotation, this process can repeatitself indefinitely with the rotor making full 360° rotations inalternatively clockwise and counterclockwise directions.

As shown in FIGS. 23-27, the ring positioning unit 20′ preferablyenables the gantry 11′ to translate and/or tilt with respect to thesupport structure. FIG. 23 shows a gantry ring positioning unit in aparked mode. FIG. 24 shows the translational motion of the positioningunit in a lateral direction relative to the cart. FIG. 25 showstranslational movement of the positioning unit in a vertical directionrelative to the cart. FIG. 26 shows the tilting motion of thepositioning unit relative to the cart. In FIG. 27, the entire gantryassembly is illustrated in fully extended lateral, vertical, and tiltpositions. The ability of the gantry to translate and tilt in multipledirections allows for the acquisition of x-ray images in any desiredprojection plane, without having to continuously reposition the patientor the system. As discussed above, a control system can automaticallymove the gantry to a desired position or orientation, including touser-defined positions and orientations stored in computer memory, forx-ray imaging procedures. X-ray scanning devices with cantilevered,multiple-degree-of-freedom movable gantries are described in commonlyowned U.S. Provisional Application No. 60/388,063, filed Jun. 11, 2002,and U.S. Provisional Application No. 60/405,098, filed Aug. 21, 2002,the entire teachings of which are incorporated herein by reference.

In the embodiments shown and described thus far, the central axis of thegantry is oriented essentially horizontally, so that an object beingimaged, such as a patient, lies lengthwise in the imaging area. In otherembodiments, however, the gantry may be aligned so that its central axisextends at virtually any angle relative to the patient or object beingimaged. For instance, the central axis of the gantry can be alignedessentially vertically, as shown in FIG. 28. Here, the central openingof the gantry is concentric with the “cylinder” formed by the torso of astanding or sitting human. The entire imaging procedure can thus beperformed while the patient remains in a standing or sitting position.Also, in addition to the medical procedures described, the vertical axisgantry may be useful for imaging other objects in which it is convenientto image the object while it is aligned in a standing or verticalorientation.

An imaging device of the present invention could also comprise asubstantially O-shaped gantry that includes a segment that at leastpartially detaches from the gantry ring to provide an opening or “break”in the gantry ring through which the object to be imaged may enter andexit the central imaging area of the gantry ring in a radial direction.An advantage of this type of device is the ability to manipulate thex-ray gantry around the target object, such as a patient, and then closethe gantry around the object, causing minimal disruption to the object,in order to perform x-ray imaging. Examples of “breakable” gantrydevices for x-ray imaging are described in commonly-owned U.S. patentapplication Ser. No. 10/319,407, filed Dec. 12, 2002, the entireteachings of which are incorporated herein by reference.

It will also be understood that although the embodiments shown hereinclude x-ray imaging devices having O-shaped gantries, other gantryconfigurations could be employed, including broken ring shaped gantrieshaving less than full 360 degree rotational capability.

While this invention has been particularly shown and described withreferences to preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the scope of the inventionencompassed by the appended claims.

For instance, although the particular embodiments shown and describedherein relate in general to x-ray imaging applications, it will furtherbe understood that the principles of the present invention may also beextended to other medical and non-medical imaging applications,including, for example, magnetic resonance imaging (MRI), positronemission tomography (PET), single photon emission computed tomography(SPECT), ultrasound imaging, and photographic imaging.

As discussed above, an x-ray scanning system is disclosed. The scanningsystem may include various embodiments which may include portions asdiscussed above and herein either separately or in combination. Forexample, FIG. 29 is a schematic diagram showing an x-ray scanning system10, such as a computerized tomographic (CT) x-ray scanner, in accordancewith one embodiment of the invention. The x-ray scanning system 10generally includes a gantry 11″ secured to a support structure, whichcould be a mobile or stationary cart, a patient table, a wall, a floor,or a ceiling. As shown in FIG. 29, the gantry 11″ is secured to a mobilecart 12″ in a cantilevered fashion via a ring positioning unit 20″. Incertain embodiments, the ring positioning unit 20″ enables the gantry11″ to translate and/or rotate with respect to the support structure,including, for example, translational movement along at least one of thex-, y-, and z-axes, and/or rotation around at least one of the x- andy-axes. X-ray scanning devices with a cantilevered,multiple-degree-of-freedom movable gantry are described in commonlyowned U.S. Provisional Applications 60/388,063, filed Jun. 11, 2002, and60/405,098, filed Aug. 21, 2002, the entire teachings of which areincorporated herein by reference.

The mobile cart 12″ of FIG. 29 can optionally include a power supply, anx-ray power generator, a computer system for controlling operation ofthe x-ray scanning device and for performing image processing,tomographic reconstruction, or other data processing functions, and adisplay system, which can include a user interface for controlling thedevice. It will be understood that one or more fixed units can alsoperform these functions.

The gantry 11″ is a generally circular, or “O-shaped,” housing having acentral opening into which an object being imaged is placed. The gantry11″ contains an x-ray source 13″ (such as a rotating anode pulsed x-raysource) that projects a beam of x-ray radiation 15″ into the centralopening of the gantry, through the object being imaged, and onto adetector array 14″ located on the opposite side of the gantry. The x-raysource 13″ is also able to rotate 360 degrees around the interior of thegantry 11″ in a continuous or step-wise manner so that the x-ray beamcan be projected through the object at various angles. At eachprojection angle, the x-ray radiation beam passes through and isattenuated by the object. The attenuated radiation is then detected by adetector array opposite the x-ray source. Preferably, the gantryincludes a detector array that is rotated around the interior of thegantry in coordination with the rotation of the x-ray source so that,for each projection angle, the detector array is positioned opposite thex-ray source on the gantry. The detected x-ray radiation from each ofthe projection angles can then be processed, using well-knownreconstruction techniques, to produce a two-dimensional orthree-dimensional object reconstruction image.

In a conventional CT x-ray scanning system, the object being imaged(typically a patient) must enter the imaging area lengthwise from eitherthe front or rear of the gantry (i.e. along the central axis of thegantry opening). This makes it difficult, if not impossible, to employCT x-ray scanning during many medical procedures, such as surgery,despite the fact that this is where CT scanning applications may be mostuseful. Also, the conventional CT x-ray scanner is a relatively large,stationary device having a fixed bore, and is typically located in adedicated x-ray room, such as in the radiology department of a hospital.CT scanning devices are generally not used in a number of environments,such as emergency departments, operating rooms, intensive care units,procedure rooms, ambulatory surgery centers, physician offices, and onthe military battlefield. To date, there is not a small-scale or mobileCT scanning device, capable of producing high-quality images atrelatively low cost, which can be easily used in various settings andenvironments, including during medical procedures.

In one aspect, the present invention relates to an improvement on theconventional design of an x-ray imaging device which overcomes these andother deficiencies. In particular, as shown in FIG. 29, the O-shapedgantry 11″ includes a segment 16″ that at least partially detaches fromthe gantry ring to provide an opening or “break” in the gantry ringthrough which the object to be imaged may enter and exit the centralimaging area of the gantry ring in a radial direction. In FIG. 29, forinstance, a segment 16″ of the gantry 11″ is secured to the gantry via ahinge 17″ which allows the segment to swing out like a door from a fullyclosed position (see FIG. 2B) to a fully open position (see FIG. 30A).The object being imaged (for instance, a patient) can then enter thegantry from the open side (as opposed to from the front or rear side ofthe gantry, as in conventional systems), and the hinged segment can thenbe reattached to fully enclose the object within the gantry ring.(Alternatively, or in addition, the gantry in the open position can bemoved towards the object in a lateral direction to position the objectwithin the imaging area, and then the open segment can close around theobject.)

In addition to the hinged door embodiment of FIGS. 29, 30A, and 30B,various other embodiments of the of the gantry assembly are shown inFIGS. 31-35. In each of these systems, a segment of the gantry at leastpartially detaches from the gantry ring to provide an opening or “break”in the gantry ring through which the object to be imaged may enter andexit the central imaging area of the gantry ring in a radial direction,and wherein the segment can then be reconnected to the gantry to perform2D x-ray or 3D tomographic x-ray imaging.

In FIG. 31, for example, a gantry segment 16″ is fully detachable fromthe fixed portion of the gantry ring 11″, and can then be reattached toperform an x-ray imaging process. Similarly, in FIG. 32, the gantrysegment 16″ fully detaches from the ring to form an opening. In thiscase, however, the detached segment “piggy backs” on the gantry. Thisembodiment may include a linkage apparatus which allows the door 16″ todetach away from the ring 11″ and, while maintaining attached to thering via the linkage apparatus, swing upwards and circumferentially ontothe top of the fixed portion of the gantry ring 11″.

FIG. 33 illustrates yet another embodiment, where the gantry opens bytelescoping the detachable segment 16″ with the fixed gantry ring 11″.In one embodiment, a the detachable segment 16″ can be attached to thegantry ring 11″ with alignment pins. A release mechanism releases thepins, and the sidewalls of the segment 16″ translate outward relative tothe gantry ring, thus allowing the segment 16″ to telescope over thefixed upper portion of the gantry ring 11″.

In FIG. 34, the gantry opens by lifting a top segment 16″ of the gantryoff the ring, preferably via a vertical lift mechanism 18″ which can belocated on the cart 12″.

FIG. 35 shows yet another embodiment with a pivoted gantry segment 16″.This is similar to the hinged design of FIG. 29, except here thedetachable segment is hinged to the gantry at the side of the gantryopposite the opening, so that the entire top half of the gantry lifts upto access the interior imaging area.

In any of these embodiments, the detachable gantry segment preferablyincludes a mechanism for securing the segment in place in a closedgantry configuration, yet also permits the segment to be easily detachedto open or “break” the gantry ring.

In FIGS. 36-38, for example, a latching assembly 18″ is used to secureor lock the hinged gantry segment 16″ in place when the gantry is closed(for instance, during an x-ray imaging process). In a locked state, thehinged segment 16″ is not permitted to pivot out from the closed gantryring, and the x-ray source 13″ and detector 14″ can rotate 360 degreesaround the inside of the closed gantry ring. However, the latchingassembly 18″ can also be easily unlocked, which permits the hingedsegment 16″ to be swung open.

In FIG. 36, for instance, the latching mechanism 18″, which includeshandle 21″, linking members 22″, 23″, and upper and lower latches 24″,25″, is in an unlocked position, while the hinged gantry segment 16″ isin a fully open position. In FIG. 37, the gantry segment 16″ is now in aclosed position, but the latching mechanism 18″ is still unlocked. Asshown in FIG. 38, the latching mechanism 18″ is locked by pulling handle21″ down into a locked position. The latching mechanism 18″ can beeasily unlocked by pushing the handle up to an unlocked position, andthe hinged gantry segment 16″ can then swing open.

In FIG. 39, the latching mechanism 18″ is shown by way of an “end on”view of the interior of the open gantry segment 16″. As shown here,spring-loaded alignment pins 34″ on the hinged gantry segment 16″ aredriven into bushings 35″ (see FIG. 36) on the fixed gantry 11″ via awedge-shaped latches 24″, 25″, causing the gantry segment 16″ to besecured to the fixed gantry portion 11″. The wedge-shaped latches24″,25″ are driven by a linkage members 22″, 23″ connected to the handle21″ operated by a user. Also shown in this figure is a slip ring 26″,which maintains electrical contact with the motorized rotor assembly 33″(see FIG. 40), and a curved rail 27″, which guides the rotor assembly33″ as it rotates around the interior of the gantry 11″, as will bedescribed in further detail below. When the gantry is in a closed andlocked position, the slip ring 26″ and curved rail 27″ of the detachablesegment 16″ align with the slip ring and curved rail of the fixedgantry, so that the motorized rotor assembly 30″ (see FIG. 40) whichcarries the x-ray source and detector array can properly rotate withinthe gantry. During operation, the slip ring 26″ preferably maintainselectrical contact with the rotor assembly 30″, and provides the powerneeded to operate the x-ray source/detector system, and to rotate theentire assembly within the gantry frame. The slip ring 26″ can also beused to transmit x-ray imaging data from the detector to a separateprocessing unit located outside the gantry, such as in the mobile cart12″ of FIG. 29.

FIGS. 43A-43E illustrate another embodiment of an x-ray imagingapparatus having a cable management system for rotating an x-ray sourceand detector array 360° around the interior of the gantry ring. In thisexample, the power for the x-ray source/detector system, as well as forrotating the x-ray source/detector within the gantry, is provided (atleast in part) by a cable harness 36″ containing one or more cables, inmuch the same manner as the slip ring described above. The cable harness36″ can also be used to transmit signals and data between the x-raysource/detector and an external processing unit.

The cable harness 36″ is preferably housed in a flexible, linked cablecarrier 37″. One end of the carrier 37″ is fixed to a stationary object,such as the gantry 11″ or the cart. The other end of the carrier 37″ isattached to the motorized rotor assembly 33″ which contains the x-raysource 13″ and detector 14″. In the example shown in FIGS. 43A-43E, therotor 33″ starts at an initial position with the x-ray source 13″ at thetop of the gantry and the detector 14″ at the bottom of the gantry (i.e.rotor angle=0°) as shown in FIG. 43A. The rotor 33″ then rotates in aclockwise direction around the interior of the gantry, as illustrated inFIG. 43B (90° rotation), FIG. 43C (180° rotation), FIG. 43D (270°rotation), and FIG. 43E (360° rotation). In FIG. 43E, the rotor 33″ hasmade a full 360° rotation around the interior of the gantry 11″, and therotor is again at the initial position with the x-ray source 13″ at thetop of the gantry, and the detector 14″ at the bottom of the gantry.During the rotation, the cable carrier 37″ remains connected to both therotor 33″ and gantry 11″, and has sufficient length and flexibility topermit the rotor 33″ to easily rotate at least 360° from the startposition. To perform another 360° rotation, the rotor 33″ can rotatecounterclockwise from the end position of the prior rotation (e.g. rotorangle=360° in FIG. 43E) until the rotor 33″ returns to the initialposition of FIG. 43A. For continuous rotation, this process can repeatitself indefinitely with the rotor making full 360° rotations inalternatively clockwise and counterclockwise directions.

FIGS. 39 and 40 show one example of a rail and bearing mechanism forrotating the x-ray source 13″ and detector 14″ inside the gantry forperforming two-dimensional and/or three-dimensional x-ray imagingprocedures. As shown in FIG. 40″, a motorized rotor assembly 33″includes the x-ray source 13″ and the detector array 14″ held within arigid frame 30″ designed to maintain a constant spacing between thesource and detector as the rotor assembly rotates inside the x-raygantry. (Note that the motorized rotor is generally c-shaped, with anopen region at least as large as the detachable segment 16″ of thegantry frame, so that the rotor assembly does not obstruct the openingof the gantry.) The rotor assembly 30″ also includes a motor 31″ andgear 32″ for driving the rotor assembly around the interior of thegantry. As shown in FIG. 39, the interior side walls of the gantryinclude curved rails 27″ which extend in a continuous loop around theinterior of the gantry when the gantry is in a closed position. The gear32″ of the rotor assembly 30″ contacts the curved rail 27″ of thegantry, and uses the rail to drive the rotor assembly around theinterior of the gantry. The rotor assembly 30″ also includes curve railcarriages 29″, which mate with the curved rails 27″ of the gantry tohelp guide the rotor assembly 30″ as it rotates inside the gantry.

The detector array 14″ shown in FIG. 40 comprises three two-dimensionalflat panel solid-state detectors arranged side-by-side, and angled toapproximate the curvature of the gantry ring. It will be understood,however, that various detectors and detector arrays can be used in thisinvention, including any detector configurations used in typicaldiagnostic fan-beam or cone-beam CT scanners. A preferred detector is atwo-dimensional thin-film transistor x-ray detector using scintillatoramorphous-silicon technology.

For large field-of-view imaging, a detector 14″ can be translated to,and acquire imaging data at, two or more positions along a line or arcopposite the x-ray source 13″, such as via a motorized detector rail andbearing system. Examples of such detector systems are described incommonly owned U.S. Provisional Application 60/366,062, filed Mar. 19,2002, the entire teachings of which are incorporated herein byreference.

FIGS. 41A, 41B, and 41C show an embodiment of the scanner assembly 10which is used for a medical imaging procedure. FIG. 41A, shows a patient40″ lying on a table 41″ next to a mobile x-ray imaging apparatus 10with a hinged segment 16″ of the gantry ring 11″ is fully open. Theentire apparatus can then be moved in a lateral direction towards thepatient (alternatively, or in addition, the patient can be moved towardsthe imaging apparatus), so that a region of interest of the patient isaligned within the x-ray gantry 11″, as shown in FIG. 41B. Finally, asshown in FIG. 41C, the hinged segment 16″ of the gantry 11″ is closed,fully enclosing the patient within the gantry ring, and an x-ray imagingprocedure is performed.

In the embodiments shown and described thus far, the central axis of thegantry is oriented essentially horizontally, so that an object beingimaged, such as a patient, lies lengthwise in the imaging area. In otherembodiments, however, the gantry may be aligned so that its central axisextends at virtually any angle relative to the patient or object beingimaged. For instance, the central axis of the gantry can be alignedessentially vertically, as shown in FIG. 42. Here, the central openingof the gantry is concentric with the “cylinder” formed by the torso of astanding or sitting human. As in the previous embodiments, the gantryincludes a segment 16″ that at least partially detaches from the gantryring 11″ to provide an opening or “break” in the gantry ring throughwhich the object to be imaged may enter and exit the central imagingarea of the gantry ring in a radial direction. The patient can enter thegantry via this opening in a standing or sitting position, and thesegment can be easily re-attached for an imaging procedure. The entireimaging procedure can thus be performed while the patient remains in astanding or sitting position. Also, in addition to the medicalprocedures described, the vertical axis gantry may be useful for imagingother objects in which it is convenient to image the object while it isaligned in a standing or vertical orientation.

The x-ray imaging apparatus described herein may be advantageously usedfor two-dimensional and/or three-dimensional x-ray scanning. Individualtwo-dimensional projections from set angles along the gantry rotationcan be viewed, or multiple projections collected throughout a partial orfull rotation may be reconstructed using cone or fan beam tomographicreconstruction techniques.

While this invention has been particularly shown and described withreferences to preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the scope of the inventionencompassed by the appended claims.

For instance, although the particular embodiments shown and describedherein relate in general to computed tomography (CT) x-ray imagingapplications, it will further be understood that the principles of thepresent invention may also be extended to other medical and non-medicalimaging applications, including, for example, magnetic resonance imaging(MRI), positron emission tomography (PET), single photon emissioncomputed tomography (SPECT), ultrasound imaging, and photographicimaging.

Also, while the embodiments shown and described here relate in generalto medical imaging, it will be understood that the invention may be usedfor numerous other applications, including industrial applications, suchas testing and analysis of materials, inspection of containers, andimaging of large objects.

The detector arrays described herein include two-dimensional flat panelsolid-state detector arrays. It will be understood, however, thatvarious detectors and detector arrays can be used in this invention,including any detector configurations used in typical diagnosticfan-beam or cone-beam imaging systems, such as C-arm fluoroscopes. Apreferred detector is a two-dimensional thin-film transistor x-raydetector using scintillator amorphous-silicon technology.

While this invention has been particularly shown and described withreferences to preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the scope of the inventionencompassed by the appended claims. For instance, although theparticular embodiments shown and described herein relate in general tocomputed tomography (CT) x-ray imaging applications, it will further beunderstood that the principles of the present invention may also beextended to other medical and non-medical imaging applications,including, for example, magnetic resonance imaging (MRI), positronemission tomography (PET), single photon emission computed tomography(SPECT), ultrasound imaging, and photographic imaging.

Also, while the embodiments shown and described here relate in generalto medical imaging, it will be understood that the invention may be usedfor numerous other applications, including industrial applications, suchas testing and analysis of materials, inspection of containers, andimaging of large objects.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the disclosure. Individual elements or featuresof a particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the disclosure, and all such modificationsare intended to be included within the scope of the disclosure.

What is claimed is:
 1. A method of operating an image apparatus,comprising: positioning a detector to image at least a portion of avolume configured to hold an object larger than a field-of-view of thedetector; utilizing a detector positioner to translate the detector tomultiple positions relative to the volume; positioning a beam such thata trajectory of the beam follows the path of the translating detector;and moving a rotor within a gantry such that the beam follows the pathof the translating detector; wherein the detector and a beam source thatemits the beam are movably mounted to the rotor.
 2. A method ofoperating an image apparatus, comprising: positioning a detector toimage at least a portion of a volume configured to hold an object largerthan a field-of-view of the detector; utilizing a detector positioner totranslatetranslating the detector to multiple positions relative to thevolume; positioning a beam such that a trajectory of the beam followsthe path of the translating detector; and driving a beam source with amotor to pivotally move the beam source mounted on a swiveling sourcemount; wherein the beam source is mounted to a source frame having atleast two separated walls and a series of lateral members extendingbetween the at least two separated walls and the swiveling source mountto pivotally hold the source relative to the source frame.
 3. A methodof operating an image apparatus, comprising: positioning a detector toimage at least a portion of a volume configured to hold an object largerthan a field-of-view of the detector; utilizing a detector positioner totranslatetranslating the detector to multiple positions relative to thevolume; positioning a beam such that a trajectory of the beam followsthe path of the translating detector; and moving a detector carriagerelative to a detector frame having at least two separated walls and aseries of lateral members extending between the at least two separatedwalls; wherein the detector is mounted to the detector carriage to holdthe detector and move the detector.
 4. The method of claim 1, furthercomprising moving separately all of the beam source, the detector, andthe rotor while obtaining images of the object.
 5. The method of claim1, further comprising rotating the rotor within an interior cavity ofthe gantry over a 360° 360 degree circumference of the gantry.
 6. Themethod of claim 1, further comprising moving a source housing within asource stage to move the source housing about a central point to directthe beam onto the detector.
 7. The method of claim 1, wherein the beamis projected by the beam source, and the trajectory of the beam isaltered by tilting the beam source.
 8. The method of claim 1, whereintranslating the detector further includes translating the detector alongan arc.
 9. The method of claim 1, wherein translating the detectorfurther includes translating the detector along a line.
 10. A method ofoperating an image apparatus, comprising: positioning a detector toimage at least a portion of a volume configured to hold an object largerthan a field-of-view of the detector, including: positioning thedetector at a first position within a gantry to image a first portion ofthe object; positioning a beam such that the beam is detected by thedetector at the first position; moving the detector to a second positionwithin the gantry to image the first portion of the object; moving thebeam such that the beam is with the detector to be detected by thedetector at the second position; and moving a rotor within the gantryfrom a first angle to a second angle; wherein both of the detector and abeam source that emits the beam are moveably mounted to the rotor. 11.The method of claim 10, further comprising: moving all of the beamsource, the detector, and the rotor to minimize exposure of the objectto radiation while obtaining images of the object.
 12. The method ofclaim 10, further comprising: moving separately all of the beam source,the detector, and the rotor while obtaining images of the object. 13.The method of claim 10, wherein moving the detector to the secondposition within the gantry includes moving the detector along an arc.14. The method of claim 10, wherein moving the detector to the secondposition within the gantry includes moving the detector along a line.15. A method of operating an imaging apparatus, comprising: positioningan object within an O-shaped gantry; rotating a rotor carrying a sourceand a detector within an interior cavity of the gantry about the object;positioning the detector to image a portion of the object that is largerthan a field-of-view of the detector; translating the detector tomultiple positions relative to the object; and positioning a beam fromthe source such that a trajectory of the beam follows the path of thetranslating detector.
 16. The method of claim 15, further comprisingutilizing a detector positioner to translate the detector to themultiple positions.
 17. The method of claim 15, wherein the detector istranslated along one of an arc or along a line.
 18. The method of claim15, further comprising tilting the source at a focal point to change thetrajectory of the beam to follow the path of the translating detector.